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October 8, 2013

Fossil Leads To Discovery Of New Evolutionary Mechanism For Body Elongation

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redOrbit Staff & Wire Reports - Your Universe Online

A third, previously unidentified reason for the extreme elongation of snake and eel bodies has been discovered by a team of University of Zurich paleontologists who published their findings Monday in the journal Nature Communications.

The lengthy, slender and flexible bodies possessed by these creatures have evolved many times independently in the over 500 million years of vertebrate animal history, the study authors explained.

Scientists had previously reported the characteristic formed in one of two ways: either through the elongation of the individual vertebrate of the vertebral column, or through the development of additional vertebrae and associated muscle segments.

Now however, University of Zurich professor Marcelo Sánchez-Villagra and his colleagues have found a third mechanism of axial skeleton elongation.

Thanks to an exceptionally well-preserved 240 million year old fossil, the investigative team was able to learn that the vertebral column of the Saurichthys curionii (an extinct genus of ray-finned fish that lived in the Triassic period) has two vertebral arch per myomeric segment, not just one.

That structure caused an elongation of the creature’s body, while also giving it a longer appearance. Erin Maxwell, a post-doctoral researcher in Sánchez-Villagra’s group, said this particular evolutionary pattern for body elongation is new.

Previously, experts had only known about the increasing number of vertebrae and muscle segments and the elongation of the individual vertebrae as methods of body elongation.

“The fossils studied come from the Monte San Giorgio find in Ticino, which was declared a world heritage site by UNESCO in 2003,” the university said in a statement. “The researchers owe their findings to the fortunate circumstance that not only skeletal parts but also the tendons and tendon attachments surrounding the muscles of the primitive predatory fish had survived intact.”

According to Maxwell, the scientists were able to determine the flexibility and the swimming aptitude of the Saurichthys curionii because of the shape and arrangement of the fossilized tendons that were discovered.

She also explained the fish genus was clearly less flexible than modern eels and unable to swim long distances at high speeds like modern oceanic fish such as the tuna. Maxwell added the one-half meter long fossilized fish is comparable to the garfish or needlefish due to its appearance and lifestyle.